1. Technical Field
The invention relates generally to chemical mechanical polishing slurries, and more particularly, to a solution for forming a polishing slurry, the polishing slurry and related methods.
2. Background Art
Chemical mechanical polishing (CMP) is a method of removing layers of solid carried out for the purpose of surface planarization and definition of metal interconnect pattern in semiconductor device fabrication. CMP includes mechanically polishing a wafer surface in a chemical slurry. 1 H-benzotriazole (BTA) is a corrosion inhibitor used in CMP slurries for copper materials. BTA is usually supplied as a solid at 98-99% purity. Commercial BTA material, however, often contains solid foreign material capable of scratching wafers. To reduce scratching, BTA is typically dissolved in a suitable solvent and filtered to remove the solid foreign material.
One approach to this filtering requirement is to dissolve the BTA in water. Water is advantageous as a solvent because it is the typical liquid medium for copper CMP slurry; hence, it does not have to be removed. Unfortunately, BTA is poorly soluble in water. As a result, filtering BTA in water requires an excessive volume of solution to be filtered, which is messy, costly and time-consuming. In addition, if the filtered solution is purchased commercially for filtering by the purchaser, a large volume of water needs to be shipped. In another approach, BTA is dissolved in solvents such as methanol, ethanol and isopropanol, in which it is highly soluble. This approach presents a number of shortcomings. For example, these solvents are not typically present in CMP slurries, and might require removal prior to use of the BTA as part of a polishing slurry. Second, the solvents are all flammable and, hence, present a flash point (safety) problem.